NOTE: Please check out https://diy.tvc-16.science/ for the definitive place for WarioWare DIY content!
This is a pretty much complete collection of user-made microgames, records, and comics for users from the USA & Japan regions that were uploaded to Nintendo Wi-Fi Connection. (these are in the proprietary .mio format the game uses). These were scraped a week before Nintendo WFC shut down by a user named "bobmcjr".
The filenames for the .mios have the creator, name, and date for each of these.